Hydraulic fluid actuated percussion tool

ABSTRACT

A hydraulic percussion tool such as a drill, a crusher or a ram, having a hammer piston reciprocating in a cylinder. A hammer piston controlled valve is arranged to pressurize and drain alternately two pressure chambers formed between the cylinder and the hammer piston so as to cause reciprocation of the hammer piston. Energy accumulators are connected directly to the pressure chambers.

United States Patent [191 Romell et al.

1 51 June 26, 1973 HYDRAULIC FLUID ACTUATED PERCUSSION TOOL [76] Inventors: Gunnar Vigg Riss Romell, 182 62 Djursholm, Smedjevagen; Ake Torsten Eklof, 127 36 Skarholmen, Satragardsvagen, both of Sweden [22] Filed: Feb. 17, 1971 [21] Appl. No.: 116,014

[52] US. Cl 91/290, 91/277, 138/31 [51] Int. Cl. F011 25/04, F011 31/00 [58] Field of Search 91/290, 291, 277;

[56] References Cited UNITED STATES PATENTS 2,780,065 2/1957 Spannhake 138/31 6/1965 Hauser 91/290 3,213,615 10/1965 Bjomberg 138/31 3,322,210 5/1967 Amdt 91 290 3,376,791 4/1968 Ashfield et a1 91/290 3,470,692 10/1969 Kamp 92/134 3,552,269 1/1971 Amdt 91/291 Primary Examiner-Paul E. Maslousky Attorney-Munson & Fiddler [5 7] ABSTRACT A hydraulic percussion tool such as a drill, a crusher or a ram, having a hammer piston reciprocating in a cylinder. A hammer piston controlled valve is arranged to pressurize and drain alternately two pressure chambers formed between the cylinder and the hammer piston so as to cause reciprocation of the hammer piston. Energy accumulators are connected directly to the pressure chambers.

4 Claims, 5 Drawing Figures mimmauuzs ms 3. 74 1; 072

sum 1 as 2 GUNNAR VIGG RISS R-"Jf-ILLL and AKE TORSTEN EKLOT,

INVEN'I'OW PAIENIEDwnzs 1915 3. 741, 072

sum 2 or 2 BY f-IUNSON & mummy:

HYDRAULIC FLUID ACTUATED PERCUSSION TOOL BACKGROUND OF THE INVENTION This invention relates to hydraulic fluid actuated percussion tools of the type which comprises a hammer which reciprocates in a cylinder and is arranged to provide shock energy in a chisel, a drill rod or the like. Particularly it relates to a tool which has a hammer piston controlled distributing valve arranged to pressurize and drain alternately two pressure chambers formed between the cylinder and the piston so as to reciprocate the hammer piston.

The flow which is necessary to provide the reciprocatory movement of the hammer piston varies periodically with the velocityof the piston and the position of the valve. As the source of pressurized hydraulic fluid is usually used a positive displacement pump, the flow of which cannot be varied in time with the movement of the piston. In prior art, the periodical variation of the flow is compensated by means of a hydraulic fluid accu-mulator in the conduit for supplying fluid to the valve. When,- during a return stroke, the valve shifts to connecting the mentioned second pressure chamber to the source of pressurized hydraulic fluid, fluid will then beurged through the valve and out into the accumulator. Therefore, the flow through the valve will momen? tarily be much larger than the flow delivered bythe pump, and the fluid" friction losses in the valve can be considerable.

It is an object of theinvention to provide an effective pressurized hydraulic fluid driven percussion toolin which kinetic energy is absorbed from the hammer piston during a part of the return stroke and returned to the hammer piston duringthe work stroke, and in which the fluid friction losses are small.

BRIEF DESCRIPTION "OF THE DRAWINGS The invention will bevdescribed inmore details with reference to the accompan'yingd'rawingsin which an embodiment of a percussion tool according to the invention is shown as' an example.

In the figures, FIG. 1'is a longitudinal section along line 11 in FIG. 2 through the percussion tool, FIG. 2 is a'transverse section along'line 22 in FIG. 1, FIG. 3 is a fragmentary longitudinal section along line 3-3 in FIG. 2, FIG. 4 isan alternative design of some details shown in FIGS. 1-3, and FIG. 5 is a circuit diagram of the percussion tool shown in FIGS. 1-3. Corresponding details have been given the same reference numeral in the various figures.

The percussion tool shown in the figures is made as a rock drill which consists ofa housing which constitutes a cylinder 11 for a reciprocating hammer piston 12. It is to be understood that the expression cylinder is used in the claims and in the specification to define the chamberin which the hammer piston reciprocates, and that the cylinder is not limited to have astraight cylindrical form, but may for instance have stepped portions. The hammer piston consists of a cylindrical rod with two piston portions 13, 14 having piston surfaces l5, 16. These piston portions have annular pressure shank 18 has mating external splines so that the drill string will rotate conjointly with the sleeve. A pressurized hydraulic fluid driven rotary motor 20, e.g. a sliding vane motor, is attached to the housing 10 and it has a drive gear 21 which rotates the sleeve 17 over a gear 22 which is partly concealed in FIG. 1. Flushing fluid is supplied to the axial hole of the drill rod 19 through a swivel'23 which is slipped onto the shank 18. The shank 18 can be moved into the sleeve .17 to abut against the axially movable anvil block 24 which then moves to a rear stop position as shown in FIG. 1. The anvil block is an anvil to the hammer piston 12 but it could be omitted and the end surface of the shank 18 bean anvil to the hammer piston. A rear annular pressure chamber 25 is defined by the cylinder 11, the rod portion 12a, the piston surface 16 on the piston portion 14, and the front surface of a sealing ridge 26. The oil that leaks through the circular clearance space between the sealing ridge 26 and the rod portion 12a is collected in a circular groove 27 which, as shown in FIG. 5, may be drained directly to tank through a conduit not shown, but, advantageously, it is drained by means of a pump so that there will be suction in the groove. By this arrangement the fluid is prevented from leaking to the closed end chamber '28 which encloses the rear end of the rod portion 12a. The cylinder 11 has another circular groove 29 to which an accumulator 30 is connected by means of a passage 31. By means of a passage 33, another accumulator 32 is connected to the cylinder 11 at the rear of the pressure groove 29.

A forward annular-pressure chamber 34 is defined in the same way by the cylinder 11, the rod portion 12b,

the piston surface '15 on the pistonportion 13, and the rear surface of a circular sealing'ridge 35. Advanta-' geously, acollectinggroove 36 is drained in the same way as the collecting groove 27. Outside the collecting equalizing grooves (shown in FIG. 5 only) which imgrooves 27, 36 sealing rings are disposed so as to seal against the. hammer piston. An accumulator 38 is connected to a circular pressure groove 37 by means of a passage 39. Each of the accumulators 30, 32, 38 has a spring-loaded piston 40 which is slidable in a cylinder. The pistons 40 of the accumulators 30, 38 are loaded by a common spring unit 41 formed by a pile of Belleville-springs braced between the piston. The piston of the accumulator 32 which is also identified by reference numeral 40 is loaded by a pile of Belleville-springs 32a.

A distributing valve in the form of a slide 42 is supplied with pressurized hydraulic fluid through a supply conduit 43. An accumulator 44 is permanently connected to the supply conduit 43 so as to receive the hydraulic fluid that is supplied when the slide 42, as shown in FIG. 2, blocks the supply conduit 43 fora short-moment when shifting position. The accumulator 44 is so loaded that it is substantially inactive at the pressures at which the accumulators 30, 38 are active. In FIG. 5, the various passages of the housing 10 are schematically illustrated. The above mentioned accumulators 30, 32, 38, 44 are in this figure shown as gas pressure loaded accumulators. The inlet 43 leads to an annular inlet chamber 45 in the cylinder of the valve.

The cylinder of the valve has also two annular outlet chambers 46, 47 to which return conduits 48, 49 are connected. These return conduits lead to a nonillustrated sump from which a non-illustrated positive displacement pump sucks hydraulic fluid so as to supply the supply conduit with a constant flow of pressurized hydraulic fluid over a non-illustrated control valve.

With the slide 42 in its righthand end position (FIG. 5), pressurized hydraulic fluid is supplied to the rear pressure chamber through a combined supply and drain passage 50 while the forward pressure chamber 34 drains to the return conduit 49 through another combined supply and drain passage 51. With the slide 42 in its non-illustrated lefthand end position, pressurized hydraulic fluid is instead supplied to the forward pressure chamber 34 through the passage 51 simultaneously as the rear pressure chamber is draining through the passage 50.

The slide 42 has projecting end portions 52, 53, the end surfaces 54, 55 of which are actuated by the pressure in control passages 56, 57 which end in the cylinder 11. The terminate portion 52 has an annular piston surface 58 which is actuated by the pressure in the passage 50 via a passage 59 in the slide, and the end portion 53 has a similar piston surface 60 which is actuated by the pressure in the passage 51 via a passage 61 in the slide. The piston surfaces 58, 60 constitute holding surfaces and are therefore of smaller area than the end faces 54, 55 which constitute shifting surfaces.

The control passage 56 has five branches which end in the cylinder 11. The reference numeral 56a denotes one of these branches. The pin 63 can be set into various positions so as to block one or several of these branches. By reason of this arrangement, the rear point of reversal of the piston and consequently the percussion energy per blow can be varied. By means ofa locking screw 64 (FIG. 3), the pin 63 can be locked in the various positions. A passage 65 is connected to drain, suitably as shown in FIG. 2, to one of the annular chambers 46, 47, so as to constantly drain the space between the piston portions 13, 14. Thus, one of the control passages 56, 57'will always be drained through this passage 65 when the other one of these control passagesis supplied with pressurized hydraulic fluid.

The operation will now be described with reference to FIG. 5.

Assume that the slide 42 is in the position shown in FIG. 5 so that the rear pressurechamber 25 is supplied with pressurized hydraulic fluid and the forward pressure chamber 34 is being drained. Assume further that the hammer piston 12 is moving forwards. The pin 63 blocks the three right branches of the control passage 56. In the position in which the hammer piston 12 is shown in FIG. 5, the control passage 57 is being drained through the draining passage 65 and the control passage 56 has been drained into the forward pressure chamber 34 all the way until the piston portion 13 has covered the branch 56a ofthe passage 56. The slide 42 is positively retained in its position because the pressure in the supply passage 50 is transmitted to the holding surface 58 of the slide. As the hammer piston 12 continues its forward movement (to the right in FIG. 5), the control passage 56 is again opened to its draining position, in this case to the drain passage 65. Thereafter, when the piston portion 14 passes the mouth of the control passage 57, its opens the latter to the rear pressure chamber 25 from which the pressure is conveyed through the control passage 57 to the end face 55 of the slide. Now, the slide shifts to its nonillustrated position (to the left in FIG. 5) so that the forward pressure chamber 34 is pressurized while the rear pressure chamber 25 is drained. This takes place just before the hammer piston strikes the anvil block 24 and the hammer piston 12 does not retard appreciably before delivering the blow. The hammer piston 12 rebounds after the impingement, but the flow of pressurized hydraulic fluid supplied through the supply passage 51 to the forward pressure chamber 34 is at the beginning larger than what can be received by the pressure chamber. Therefore, the accumulator 38 receives fluid at the beginning, but when the hammer piston 12 has reached the speed which corresponds to the flow supplied by the pump, the accumulator 38 starts discharging to the pressure chamber 34 and thus further increases the speed of the hammer piston 12. The slide 42 remains in its lefthand position because the pressure in the supply passage 51 is conveyed to the holding surface 60 of the slide. The control passage 57 is already in communication with the drain passage 65 when the piston surface 15 of the piston portion 13 passes the branch passage 56a of the control passage 56 so that the pressure of the forward pressure chamber 34 is transmitted through the control passage 56 to the end face 54 of the slide. The slide 42 shifts therefore into its righthand position (shown in FIG. 5) where it remains because of the fluid pressure upon the holding surface 58. Pressurized hydraulic fluid is now supplied from the inlet 43 to the rear pressure chamber 25 and the hammer piston 12 retards due to the hydraulic fluid pressure upon the piston surface 16. The accumulator 30 now receives the hydraulic fluid flow supplied through the supply conduit as well as the hydraulic fluid that is forced out from the pressure chamber 25 because of the rearward movement of the hammer piston 12 which decreases the volume of the pressure chamber 25. During normal return strokes, the hammer piston 12 reverses its movement because of the pressure in the rear pressure chamber 25 before moving so far to the rear that the piston surface 16 reaches the rear edge of the groove 29, and the accumulator 30 is therefore continuously in communication with the pressure chamber 25. The accumulator 32 is so loaded as to be inactive during this operation. The accumulator 30 is also supplied with pressurized hydraulic fluid during the first part of a work stroke since the pressurized fluid flow through the supply passage 50 is larger at the beginning than what the pressure chamber 25 can receive. However, when the hammer piston 12 reaches the speed that corresponds to this supplied flow, the accumulator 30 starts instead to supply pressurized hydraulic fluid to the pressure chamber 25 and thus increases the speed of the hammer piston further.

Thus, kinetic energy of the hammer piston from the return stroke is stored in the accumulator 30 and this energy is delivered back to the hammer piston during the succeeding work stroke.

If the drill rod shank 18 should not be pressed against the anvil block 24 or if no shank 18 should have been inserted through the sleeve 17, then the hammer piston will not rebound even if the anvil block 24 should happen to be in the rear position, but the hammer piston will then pass by its normal forward point of reversal and its piston surface 15 will pass by the groove 37 so that the accumulator 38 and the supply passage 51 both are shut off from the forward pressure chamber 34 which now acts as a damping chamber. However, the supply passage 51 is still in communication with the accumulator 38 through the pressure groove 37. The pressure in the pressure chamber/damping chamber 34 is now instantaneously increased for instance to a pressure two or three times the pump pressure. Thereby, hydraulic fluid flow is forced to the rear through the clearance space between the piston portion 13 and the cylinder 11 and out into the pressure groove 37. Simultaneously the slight amount of hydraulic fluid which passes by the sealing ridge 35 out into the collecting groove 36 is increased. The hammer piston 12 will therefore be braked to a quiet but cushioned stop. Owing to leakage past the piston portion 13 from the pressure groove 37 to the pressure chamber 34, the hammer piston 12 will then move slowly rearwardly until the piston surface 15 reaches the pressure groove 37, whereupon the hammer piston 12 starts to accelerate to its normal return stroke.

The hammer piston 12 may get an exceptionally hard rebound from the anvil block 24 after certain impacts. This happens especially if the percussion tool is used as a feather and wedge device for splitting a stone block. If the percussion energy in a specific blow is too small to split the stone block, as much as 80 percent of the percussion energy may be returned to the hammer piston as kinetic energy. This results in the speed of the hammer piston 12 being so high that the piston surface 16 passes the pressure groove 29, and thus the accumulator 30 and the supply passage 50 both become closed off from the rear pressure chamber 25. However, the supply passage 50 will still be in communication with the accumulator 30 by means of the pressure groove 29. The two accumulators 30 and 38 should have level characteristic curves since they are connected to the inlet 43 from the pumpv all the time they are active; i.'e.

they should be so loaded that the hydraulic fluid pres-- sure therein increases slowly with the accumulated hydraulic fluid amount. The accumulator 32, on the other hand, can preferably have a very steep characteristic curve and, furthermore, it may be so loaded that it is inactive until the point where the pressure in the pressure chamber substantially exceeds thepump pressure. As a result, the pressure in the pressure chamber 25 increases instantaneously to a degree which for instance may be twice the pump pressure when the piston'surface 16 passes the pressure groove 29 before the accumulator 32 starts receiving any hydraulic fluid. The result is that the hammer piston 12 is braked to a stop very rapidly, but with a cushioned effect, by the accumulator 32, and this braking energy is returned to the hammer piston 12 in the succeeding work stroke.

Therefore, the hammer piston 12 will now transmit to the anvil block a percussion energy, which is considerably larger than that of a normal blow. The distance of the piston travel will not be substantially increased because of the high braking pressure in the accumulator 32.

The advantage of this automatic and very large increase in percussion energy when a normal stroke is not sufficient is very important especially in connection with large crushers or rams designed to be mounted on the arm of a digging machine or the like. The rotary motor is of course not necessary in a crusher or ram according to the invention, but the attachment of the work tool can be simplified compared with the attachment of the drill shown in the figures.

According to the invention, the two accumulators 30 and 32 can be replaced by a two-stage accumulator which, instead of the accumulator 32, is connected to the passage 33. Such a two-stage accumulator is schematically shown in FIG. 4. The spring 66 corresponds to the spring which loads the accumulator 30, and the spring 67 corresponds to the spring which loads the accumulator 32.

The invention can also be varied in other wayswithin the scope of the claims. 1

What I claim is:

1. A hydraulic fluid actuated percussion tool comprising a housing forming a cylinder, a hammer piston reciprocable in the cylinder between a forward percussion stroke and a rearward rebound stroke to deliver percussion energy to a work tool, a first variable volume pressure chamber in said cylinder for urging the piston forward during the percussion stroke defined between the piston and the cylinder, a second variable volume pressure chamber in said cylinder for urging the piston rearward during the rebound stroke defined between the piston and the cylinder, valve means connected to a source of pressurized hydraulic fluid and to said first chamber by first passage means and to said second chamber by second passage means for cyclically pressurizing and draining said chambers to receiprocate the hammer piston, a first accumulator connected to said first passage means and to said first pressure chamber for storing kinetic energy from the rearward rebound strokes of a predetermined normal percussion force of the piston and reversing it to the forward percussion strokes, a second fluid accumulator connected to said first pressure chamber at a point located rearwardly of the connection of said first passage means to the first pressure'chamber, said second accumulator being normally inactive to reciprocate the piston at the motive pressure of the hydraulic fluid while being effective to reverse said piston to the forward percussion stroke at pressures higher than the motive pressure of the hydraulic fluid, produced by the hammer piston overtravelling its normal rearward reversing point so as to cover said first passage means when rebounded by a percussion stroke exceeding the normal percussion force. 7

2. A tool as claimed in claim 1 in which said passage for supplying fluid to said first pressure chamber and the passage to the first accumulator terminate in a common annular groove in the cylinder.

3. A hydraulic fluid actuated percussion tool comprising a housing forming a cylinder, a hammer piston reciprocable in the cylinder between a forward percus-. sion stroke and a rearward rebound stroke to deliver percussion energy to a work tool, a first variable volume pressure chamber for urging the.piston forward during the percussion stroke defined between the piston and the cylinder, a second variable volume pressure chamber for urging the piston rearward during the rebound stroke defined between the piston and the cylinder, hammer piston controlled distribution valve means connected to a source of pressurized hydraulic fluid, to the first pressure chamber by means of a first connection passage, and to the second pressure chamber by means of a second connection passage, the distribution valve means having a first position in which it pressurizes the first connection passage and drains the second and a second position in which it drains the first connection passage and pressurizes the second connection passage, the hammer piston actuating the valve means to shift from the second position to the first position while moving rearward during the rebound stroke and actuating the valve means to shift from the first to the second position when close to its impact position, a first accumulator connected to said first supply passage for storing kinetic energy from the rebound strokes of the piston of a predetermined normal percussion force and reversing it to the forward percussion strokes, a second fluid accumulator connected to said first pressure chamber at a point located rearwardly of the connection of said first supply passage to the first pressure in a common annular groove in the cylinder.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION iatent No. 3 i 741 I D d June 26 r 1973 lnventofls) Gunnar Vigg Riss Romell and Ake Torstexi Eklof It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[73] Assignee ATLAS COPCO AKTIEBOLAG FOREIGN APPLICATION PRIORITY DATA 19 Sweden.... ..-....2090/l970 Signed and sealed this 23rd day of July 197 (SEAL) Attest:

MCCOY M. GIBSON, JR. 0. MARSHALL DANN Commissioner of Patents Attesting Officer USCOMM-DC 60376-P69 r u.s GOVERNMENT PRINYING OFFICE: IlI o-aae-au FORM PO-IOSO (10-69) 

1. A hydraulic fluid actuated percussion tool comprising a housing forming a cylinder, a hammer piston reciprocable in the cylinder between a forward percussion stroke and a rearward rebound stroke to deliver percussion energy to a work tool, a first variable volume pressure chamber in said cylinder for urging the piston forward during the percussion stroke defined between the piston and the cylinder, a second variable volume pressure chamber in said cylinder for urging the piston rearward during the rebound stroke defined between the piston and the cylinder, valve means connected to a source of pressurized hydraulic fluid and to said first chamber by first passage means and to said second chamber by second passage means for cyclically pressurizing and draining said chambers to receiprocate the hammer piston, a first accumulaTor connected to said first passage means and to said first pressure chamber for storing kinetic energy from the rearward rebound strokes of a predetermined normal percussion force of the piston and reversing it to the forward percussion strokes, a second fluid accumulator connected to said first pressure chamber at a point located rearwardly of the connection of said first passage means to the first pressure chamber, said second accumulator being normally inactive to reciprocate the piston at the motive pressure of the hydraulic fluid while being effective to reverse said piston to the forward percussion stroke at pressures higher than the motive pressure of the hydraulic fluid, produced by the hammer piston overtravelling its normal rearward reversing point so as to cover said first passage means when rebounded by a percussion stroke exceeding the normal percussion force.
 2. A tool as claimed in claim 1 in which said passage for supplying fluid to said first pressure chamber and the passage to the first accumulator terminate in a common annular groove in the cylinder.
 3. A hydraulic fluid actuated percussion tool comprising a housing forming a cylinder, a hammer piston reciprocable in the cylinder between a forward percussion stroke and a rearward rebound stroke to deliver percussion energy to a work tool, a first variable volume pressure chamber for urging the piston forward during the percussion stroke defined between the piston and the cylinder, a second variable volume pressure chamber for urging the piston rearward during the rebound stroke defined between the piston and the cylinder, hammer piston controlled distribution valve means connected to a source of pressurized hydraulic fluid, to the first pressure chamber by means of a first connection passage, and to the second pressure chamber by means of a second connection passage, the distribution valve means having a first position in which it pressurizes the first connection passage and drains the second and a second position in which it drains the first connection passage and pressurizes the second connection passage, the hammer piston actuating the valve means to shift from the second position to the first position while moving rearward during the rebound stroke and actuating the valve means to shift from the first to the second position when close to its impact position, a first accumulator connected to said first supply passage for storing kinetic energy from the rebound strokes of the piston of a predetermined normal percussion force and reversing it to the forward percussion strokes, a second fluid accumulator connected to said first pressure chamber at a point located rearwardly of the connection of said first supply passage to the first pressure chamber and being normally inactive at the motive pressure of the hydraulic fluid while effective to reverse said piston to its forward percussion stroke at pressures higher than the motive pressure of the hydraulic fluid, produced by the hammer piston overtravelling its normal rearward reversing point so as to cover said first passage means upon rebound from a percussion stroke exceeding the normal percussion force.
 4. A tool as claimed in claim 3 in which said supply passage for supplying fluid to said first pressure chamber and the passage to the first accumulator terminate in a common annular groove in the cylinder. 